import type { ApolloServerPlugin } from "@apollo/server";
import { getComplexity, simpleEstimator } from "graphql-query-complexity";
import { GraphQLError } from "graphql";

interface QueryComplexityPluginOptions {
  maxComplexity?: number;
  defaultComplexity?: number;
}

/**
 * Apollo Server Plugin für Query Complexity Limits
 * Verhindert zu komplexe Queries, die das System überlasten könnten
 */
export const queryComplexityPlugin = (
  options: QueryComplexityPluginOptions = {}
): ApolloServerPlugin => {
  const maxComplexity = options.maxComplexity ?? 1000;
  const defaultComplexity = options.defaultComplexity ?? 1;

  return {
    async requestDidStart() {
      return {
        async didResolveOperation({ request, document, schema }) {
          if (!schema) return;

          try {
            const complexity = getComplexity({
              schema,
              operationName: request.operationName || undefined,
              query: document,
              variables: request.variables || {},
              estimators: [
                // Basis-Komplexität für jeden Field
                simpleEstimator({ defaultComplexity }),
              ],
            });

            // Speichere Complexity im Request für Monitoring
            (request as any).complexity = complexity;

            if (complexity > maxComplexity) {
              throw new GraphQLError(
                `Query zu komplex (${complexity}). Maximum: ${maxComplexity}`,
                {
                  extensions: {
                    code: "QUERY_TOO_COMPLEX",
                    complexity,
                    maxComplexity,
                  },
                }
              );
            }
          } catch (error: any) {
            // Wenn es ein Schema-Realm-Problem gibt, logge es aber blockiere nicht
            if (error.message?.includes("another module or realm")) {
              console.warn(
                "[Query Complexity] Schema-Realm-Konflikt, Complexity-Check übersprungen"
              );
              return;
            }
            throw error;
          }
        },
      };
    },
  };
};